The present invention relates to a heat dissipater for integrated circuits.
Over the past few years, the ever greater development of the potential of integrated circuits has led, in parallel, to the need to have available appropriate means for their cooling, due to the considerable amount of heat that is generated therein.
A feature shared by all heat dissipation devices known to date is that of comprising a dispersion element made of a conducting material that is brought into contact with the upper surface of the integrated circuit. The thermal contact may be accentuated by means of appropriate heat-conducting pastes, which are interposed between the integrated circuit and the dispersion element.
Additionally, to the upper part of the dispersion element can be associated a fan to enhance heat exchange.
Over time, quite a number of systems for coupling the dispersion elements to the integrated circuits have been developed.
A first type of design, described in many variations for instance in the Patents U.S. Pat. Nos. 5,313,099, 5,397,919, 5,667,870, 5,825,622, 5,774,335, 6,014,315, 5,945,736, 6,021,045, 6,075,699, and 6,252,774, provides for the dissipater to be constituted by a support that is fixed relative to the integrated circuit, and by a dispersion element with cylindrical base that is screwed in an appropriate seat obtained in the support in correspondence with the upper surface of the integrated circuit.
The support can be fastened either directly on the integrated circuit, by means of a pressure coupling or of a lateral sliding of the support on the integrated circuit itself, or using appropriate holes or supports obtained in the board whereon the integrated circuit is mounted.
This first dissipater design type, however, has a series of drawbacks.
In particular, dissipaters built as described above have a limited dispersion power, because they do not allow to obtain the thermal contact between the dispersion element and the integrated circuit over the entire surface of the circuit, because of the cylindrical shape of the base of the dispersion element. An additional drawback is constituted by the fact that the pressure exerted by the dispersion element against the integrated circuit depends on how far the assigned operator screws the dispersion element itself on the support.
It should be kept in mind that the amount of tightening must be appropriately calibrated, because an insufficient tightening compromise conduction between the two, whilst an excessive tightening can lead to the warping of the integrated circuit.
A second heat dissipater design type provides for the dispersion element to have a rectangular base surface corresponding to the upper surface of the integrated circuit, whereto it is fastened by means of appropriate mounting clips or mounting hooks.
The mounting clips are fastened inferiorly either to the integrated circuit or to the circuit whereon it is mounted, at the two sides of the dispersion element, and they press it downwards from above.
The pressure of the clip against the dispersion element can be effected by means of a thrust element screwed into the clip itself, as described for instance in the U.S. Pat. Nos. 5,784,257 and 5,774,335, by means of a manually operated cam as described for instance in the U.S. Pat. No. 6,201,697, by means of appropriate springs as disclosed for instance in the Patent GB 2312986, or by means of an elastic action of the clip itself as described for instance in the U.S. Pat. Nos. 4,857,595, 5,818,695.
In regard to the hooks, they fasten in different points (for instance in the four corners) the dispersion element either to the board or to the integrated circuit, and they are occasionally aided by thrust means (springs or screws) which press the dispersion element against the integrated circuit, as described for instance in the U.S. Pat. Nos. 6,061,240 and 6,055,159.
The main drawback of this second dissipater design type consists of the difficulties encountered during the mounting phase, when the installer has a plurality of distinct pieces to be applied simultaneously.
This drawback is accentuated by the fact that oftentimes the integrated circuits that require cooling (such as microprocessors) are mounted on the related boards with very little space between the various components, so that there is hardly any room to manoeuvre.
If the pressure on the dispersion element is effected by means of screwing, all the drawbacks mentioned above for the direct screwing of the dispersion elements are also encountered.
A further drawback, common to all types described both of the first and of the second set of solutions wherein the dissipater is fastened directly to the board, is constituted by the fact that mounting said dissipaters requires the structural modification of the board, so that the dissipaters cannot be applied to existing integrated circuits mounted on boards lacking the appropriate holes or supports.
An alternative embodiment is described in the U.S. Pat. No. 6,093,961. In this case the heat dissipater is constituted solely by the dispersion element which inferiorly has appropriate appendages provided with pins that allow for their direct fastening to the integrated circuit.
The coupling can be either of the irreversible, pressure type, or of the reversible type. In this latter case the pins are located at the end of a lever that can be operated by a user in such a way that the pins are rotated about the fulcrum point of the lever, from an open position in which the dissipater can be mounted on the integrated circuit to a closed position in which the dissipater remains locked to the integrated circuit.
Although in this second case the pins are inclined in such a way as to press the dispersion element against the integrated circuit, with the embodiment described in the U.S. Pat. No. 6,093,961 it is not possible to obtain a pressure that is sufficiently uniform and constant over time between the dispersion element and the integrated circuit.
An additional embodiment is described in the U.S. Pat. No. 5,396,402 (FIGS. 6 through 8).
In this case the dissipater is constituted by a dispersion element whose dimensions substantially coincide with those of the upper part of the integrated circuit, and by means for coupling the dispersion element to the integrated circuit, means which in turn are constituted by two locking elements mounted on two opposite sides of the dispersion element.
Each locking element is pivotally engaged to the dispersion element by means of an appropriate coupling inserted between two tabs of the dispersion element itself, and it inferiorly has a pin able to be secured underneath the integrated circuit.
The locking element can rotate from a coupled position to an uncoupled position. Appropriate springs placed on a tab force the rotation of the locking element towards the coupled position.
The main drawbacks of this solution are, on one hand, the poor mechanical rigidity of the dissipater whose parts are not mutually fastened in a stable fashion, on the other hand the poor pressure that can be exerted with the spring. Due to the rotary motion, only a part of the force exerted by the spring can be exploit to exert a pressure between the dispersion element and the integrated circuit.
In this situation the technical task constituting the basis of the present invention is to obtain a heat dissipater for integrated circuits that is alternative with respect to prior art ones, and that overcomes the aforementioned drawbacks.
In particular, a technical task of the present invention is to obtain a heat dissipater for integrated circuits, that has a solid structure and guarantees a calibrated pressure of the dispersion element against the integrated circuit.
Another technical task of the present invention is to obtain a heat dissipater for integrated circuits that is easily mounted on an integrated circuit and equally easily removed therefrom.
A further technical task of the present invention is to obtain a heat dissipater for integrated circuits that guarantees an excellent heat dissipation and that may be associated to a cooling fan.
The specified technical task and the indicated aims are substantially achieved by a heat dissipater for integrated circuits, as described in the accompanying claims.